1. Field of the Invention
The present invention relates to a method for fabricating carbon nanotubes and carbon nano particles, and more particularly, to a method for fabricating carbon nanotubes and carbon nano particles which can easily separate from each other.
2. Description of Related Art
Carbon nanotube is a key-material for nano-technology, but for the recent technology, the cost of manufacturing industrial carbon nanotube is still very high.
In today's main carbon nanotube process, a silicon, SiO2 or Al2O3 substrate is first provided, which is filled with metal-catalyst. The metal-catalyst, having transitional metals such as Fe, Co, Ni, or alloys thereof, is a metal film deposited by coating process, and then the catalyzed metal film is converted into nano-size metal-catalyst particles. Afterwards, the substrate having metal-catalyst particles is placed into a CVD (chemical vapor deposition) system or MPCVD (microwave-plasma-enhanced chemical vapor deposition) system and exposed to carbon-containing gases (e.g. acetylene, methane), so as to make carbon-containing gases pyrolysize at high temperature or ionize into carbon, then the carbon can be absorbed to the surface of the metal-catalyst particles and is deposited to provide a carbon nanotube.
However, the substrate using metal-catalysts should form a plurality of holes on the surface of the substrate, and those metal-catalysts should be placed into holes, so the process widely increases the difficulties, complexity, and cost of manufacturing.
On the other hand, after the growing of the carbon nanotube, the carbon nanotube collected from the substrate can be further mixed with conductive metal-paste (e.g. silver paste), followed by using a screen-printing process to coat onto another substrate, which is then applied to the cathode of the large-size field emission display panel. Hence the problem that the carbon nanotube aggregates and is not easily separated because of the aspect ratio and the nanoscale of the carbon nanotube, result in decreasing the uniformity of the carbon nanotube. As can be seen, non-uniform distribution of the carbon nanotube will cause great non-uniformity of field emission current, which may further influence the brightness quality of field emission display panel.